Display racks in stores accommodate diverse products for consumers to choose from. In order to clearly notify customers of names, prices or other data of the products, stickers are usually disposed in front of the products for labeling the names, prices or other data of the products. However, prices are adjusted often and positions of products also change often, therefore great amount of labor is required to replace the stickers. Replacing stickers is prone to delay and error. Moreover, stickers can fall off from the racks.
Currently, electronic shelf labels (ESL) and electronic paper are used to display product data, replacing the practice of using stickers as labels. However, electronic shelf labels and electronic papers have limited resolution and cannot display color images. Due to these limitations, electronic shelf labels and electronic papers are constrained to displaying product names, prices, and few other data.
Additionally, TIPO publications TW 1231401, TW 1243276, TW 1287119, TW 1283793, TW 1275895, TWM327045,TW M328591 and TIPO application TW 104101729 discloses features relating to projection devices. Also, SIPO publication CN 101773346, USPTO publications U.S. Pat. Nos. 7,832,874 and 8,047,657, and USPTO application 20130176398 further discloses arranging projection devices on display racks. However, these techniques require arranging of a reflective mirror between a projection device and a projection screen on a display rack, for reflecting light from the projection device onto the projection screen to display image frames. Application of reflective mirrors not only increases cost and space needed for accommodation, but also need to be precisely arranged in spite of potential outside impact which display racks are susceptible to. Therefore, doing away with reflective mirrors arranged between projection devices and projection screens on display racks is a problem to be solved.